The Australian DJs who made a prank call to the hospital treating the Duchess of Cambridge will not be prosecuted.

No charges will be brought against Mel Greig and Michael Christian over the hoax, the Crown Prosecution Service said.

Details of the Duchess' rare form of morning sickness were revealed on air on December 4, 2012, when the pair made the prank call to King Edward VII's Hospital in central London, posing as the Queen and Prince Charles.

Nurse Jacintha Saldanha transferred them to a colleague, who then described Kate Middleton's condition in detail.

Ms Saldanha, a mother of two, was found hanged three days later in her living quarters at the hospital, sparking a backlash against the 2Day FM DJs.

Malcolm McHaffie, from the CPS, said there was no evidence to support a manslaughter charge and any potential prosecution would not be in the public interest.

Mother-of-two Jacintha Saldanha and her husband Ben Barboza

Scotland Yard provided the CPS with a file of evidence on December 19 and asked advice on whether a prosecution should be brought.

Mr McHaffie said the CPS had taken into account, among other matters, that it is not possible to extradite people from Australia on the potential offences in question.

He also said it considered that "however misguided, the telephone call was intended as a harmless prank".

"The consequences in this case were very sad. We send our sincere condolences to Jacintha Saldanha's family," he added.

John Lofthouse, chief executive at King Edward VII's Hospital, said it would not be commenting on the matter.

He added: "The consequences of that hoax call are well-known, and tragic. We will continue to support the family of our much-loved nurse Jacintha Saldanha during what continues to be a very sad time."

Earlier this week, Southern Cross Austereo, the parent company of the radio station 2Day FM, announced the DJs would be keeping their jobs and returning to the air soon "in roles that make full use of their talents".

The DJs apologised and expressed their regrets in emotional television interviews after Ms Saldanha's death, saying they never expected their call would be put through.

Hot 30 - the show they hosted, was taken off air and later cancelled.

Ms Saldanha's inquest, which was opened in December, is due to resume on March 26.